BURLINGTON — A Vermont Medical Practice Board investigator and a former Immigration and Customs Enforcement agent have been charged with federal gun and tax violations.

Phil Ciotti, 56, of the medical board, was named in a six-count grand jury indictment Thursday. He faces charges of failing to keep required records regarding gun sales as a federal firearms licensee; failing to contact the national instant criminal background check system in connection with the sale of a firearm as well as filing false tax returns.

Richard Bernholz, the former ICE agent, agreed to plead guilty to filing a false tax return and aiding and abetting in the failure to keep adequate records by a federal firearms licensee.

In 2011, agents seized more than 500 guns from Ciotti’s St. Johnsbury home and more than 150 guns from Bernholz’s Franklin home. They said the guns were used in a Boston homicide and a Brockton shooting.

Ciotti’s defense lawyer, David Sleigh of St. Johnsbury, said his client plans to plead not guilty.

“There is a divergence of opinions for some time whether there was any criminal conduct,” he told the Burlington Free Press.

He said federal officials have singled out Ciotti for some reason.

A lawyer representing Bernholz didn’t return a phone message. No arraignment dates have been scheduled.